What happens when you hit the gym, dig into a practice or head out to set your best mile time? Aside from that familiar increase in blood flow, you immediately become acquainted with the numbers that attach themselves so tightly to perceived performance.

Every machine at the gym flickers methodically while processing a whole slew of exercise variables. Heart rate monitors beep away, filling you in on cardiovascular strain and whether or not you’re pushing as “hard” as you were yesterday. Your coach shouts that you’re 12 seconds slower than your teammate.